Canola protein isolates can be formed from canola oil seed meal. In copending U.S. patent application Ser. No. 10/137,391 filed May 3, 2002 (WO 02/089597), assigned to the assignee hereof and the disclosure of which is incorporated herein by reference, there is described a method of making canola protein isolates from canola oil seed meal, such isolates having at least 100 wt % protein content (N×6.25). The procedure involves a multiple step process comprising extracting canola oil seed meal using a salt solution, preferably an aqueous sodium chloride solution, separating the resulting aqueous protein solution from residual oil seed meal, increasing the protein concentration of the aqueous solution to at least about 200 g/L while maintaining the ionic strength substantially constant by using a selective membrane technique, diluting the resulting concentrated protein solution into chilled water to cause the formation of protein micelles, settling the protein micelles to form an amorphous, sticky, gelatinous gluten-like protein micellar mass (PMM), and recovering the protein micellar mass from supernatant, the PMM having a protein content of at least about 100 wt % as determined by Kjeldahl nitrogen (N)×6.25. As used herein, protein content is determined on a dry weight basis. The recovered PMM may be dried.
In one embodiment of the process described above and as specifically described in application Ser. No. 10/137,391, the supernatant from the PMM settling step is further processed to recover a protein isolate comprising dried protein from the wet PMM and supernatant. This procedure may be effected by initially concentrating the supernatant using ultrafiltration membranes, mixing the concentrated supernatant with the wet PMM and drying the mixture. The resulting canola protein isolate has a high purity of at least about 90 wt % of protein (N×6.25), preferably at least about 100 wt % protein (N×6.25).
In another embodiment of the process described above and as specifically described in application Ser. No. 10/137,391, the supernatant from the PMM settling step is processed to recover a protein isolate from the supernatant. This procedure may be effected by initially concentrating the supernatant using ultrafiltration membranes and drying the concentrate. The resulting canola protein isolate has a high purity of at least about 90 wt % protein (N×6.25), preferably at least about 100 wt % protein (N×6.25).
The procedures described in the aforementioned U.S. patent applications are essentially batch procedures. In copending U.S. patent application Ser. No. 10/298,678 filed Nov. 19, 2002 (WO 03/043439), assigned to the assignee hereof and the disclosures of which are incorporated herein by reference, there is described a continuous process for making canola protein isolates. In accordance therewith, canola oil seed meal is continuously mixed with a salt solution, preferably aqueous sodium chloride solution, the mixture is conveyed through a pipe while extracting protein from the canola oil seed meal to form an aqueous protein solution, the aqueous protein solution is continuously separated from residual canola oil seed meal, the aqueous protein solution is continuously conveyed through a selective membrane operation to increase the protein content of the aqueous protein solution to at least about 200 g/L while maintaining the ionic strength substantially constant, the resulting concentrated protein solution is continuously mixed with chilled water to cause the formation of protein micelles, and the protein micelles are continuously permitted to settle while the supernatant is continuously overflowed until the desired amount of PMM has accumulated in the settling vessel. The PMM is removed from the settling vessel and may be dried. The PMM has a protein content of at least about 90 wt % as determined by Kjeldahl nitrogen (N)×6.25, preferably at least about 100 wt % (N×6.25).
As described in the aforementioned U.S. patent application Ser. No. 10/137,391, the overflowed supernatant may be processed to recover canola protein isolate therefrom.
As described in copending U.S. patent application Ser. No. 10/413,371 filed Apr. 15, 2003 and corresponding PCT Publication No. WO 03/088760, assigned to the assignee hereof and the disclosures of which are incorporated herein by references, the PMM-derived canola protein isolate consists predominantly of the 7S protein along with some 12S protein while the supernatant-derived canola protein isolate consists predominantly of the 2S protein.
Oil seed meals, including canola oil seed meal, contain anti-nutritional factors, including phytic acid, often present in salt form as phytates. The term “phytic acid” used herein includes such salt forms. Depending on the oil seed, the content of phytic acid in oil seed meals may range from about 0.3 to about 10 wt %. Typically, canola oil seed meal contains about 2 to about 6 wt % of phytic acid.
Extraction of the canola oil seed meal with aqueous sodium chloride solution to form an aqueous protein solution solubilizes anti-nutritional factors including phytic acid from the oil seed meal, which results in the presence of phytic acid in the protein isolate recovered from the aqueous protein solution. As the quantity of phytic acid in the protein isolate increases, the digestibility of the protein isolate is adversely affected. The digestibility of the protein isolate is important in certain applications including aquaculture. It is desirable, therefore, to decrease the phytic acid content of the protein isolate for such applications.
Canola is also known as rapeseed or oil seed rape.